SCP Foundation

So at the time I wrote this, I'd only read through half of your draft. However, this problem had appeared twice and it really needs to be addressed as soon as possible. Consider this sentence:

In the event of SCP-XXXX taking form, Mobile Task Force Chi-57 ("Paper Shredders") are to be sent to terminate the subject being targeted by SCP-XXXX and the form SCP-XXXX takes before further instances of SCP-XXXX-A can be created, a cover up story is to be created, all instances of SCP-XXXX-A destroyed, and finally all witnesses, including foundation personnel, are to be given A-class anesthetics.

Yes. That is one, giant run-on sentence. Besides being incorrect, sentences like this end up reading as disorganized and messy, since there's no real subject being addressed. When you come across sentences like this, I recommend that you split them up into coherent, concise sentences. Let's consider this one as an example and I'll leave the others to you.

If you read this example carefully, you will also notice corrections to smaller grammatical mistakes that still need to fixed. For example, referring to Mobile Task Force Chi-57 in the plural form is incorrect (are should be is) and SCP-XXXX-A instances are to be destroyed, not just "instances of SCP-XXXX-A to be destroyed."

To be quite honest, I lost interest in this draft once I learned that this was an impossible to contain entity that preyed off people's worst fears. Being impossible to contain is already risky because it's not very interesting to read, and it's difficult to justify properly. In your case, it doesn't really feel justified. So this thing kills someone and takes their form? Then why not imprison the next time the dead person reappears somewhere? You don't describe the extensive psychic and telekinetic powers but I imagine the Foundation can tie this thing up and/or drop a box on it.

The entity that uses people's worst fears is also rather boring. "Worst fear" is a concept that's really risky to play around with since it often comes across as a catch-all term that circumvents in-depth description. For example, an entity that infects someone with a specific, yet paralyzing fear of…refrigerators(as an example) offers more opportunity to be descriptive because the author can extensively write about how terrifying it would be to be locked in one, or have one fall on top of you, or slam shut while you're reaching for food. Terror can be evoked because the other has a specific target: make people afraid of refrigerators. With worst fears, however, you are simply stating that something takes the form of one's "worst fear" and hoping the reader can do the rest of the work by imagining their worst fear. This doesn't usually work because reader mental pictures are more readily formed and better created when powerfully described.

I recommend seriously reconsidering using these two as the foundation pillars of your SCP.

All documents, articles, literature, art pieces, and even audio recordings that mention SCP-XXXX

I don't think it's really commonplace that letters and packages talking about "SCP-XXXX" are being spread around everywhere. This is unrealistic. If SCP-XXXX goes by another name, such as Boondewoogle, then the Pony Express only has to intercept the mail that has that name written in it, which affects your procedures.